While a number of prior art watercraft portage devices have been proposed to effectively transport small boats and watercraft to and from the water's edge, each of these devices, while having served a particular purpose have also exhibited a number of drawbacks. U.S. Pat. No. 5,197,405 describes a boat-attached wheel system that positions both wheels as a single unit and stows them behind the transom, with no flexibility in choosing wheel position independently. This causes interference with transom-mounted motors and other apparatus such as “ski ropes”.
U.S. Pat. No. 3,499,177 shows a boat-attached wheel system requiring that the boat be inverted to roll the boat on land or into the water. Since the boat cannot operate inverted in the water, it requires that the boat be inverted prior to water entry. This requires lifting or rolling the boat to an upright position, and carrying or sliding the boat into the water instead of simply rolling the boat into the water such as the present invention.
U.S. Pat. No. 5,261,680 shows a boat-attached wheel system that is not adjustable. It only fits one boat width, is not adjustable longitudinally to compensate for longitudinal changes in boat loading, does not have the ability to retract the wheel assemblies into horizontal or vertical positions, and requires storage of wheels inside the boat where they take up passenger space and may get the passenger(s) wet.
U.S. Pat. No. 4,515,102 shows a wheel-axle arrangement with a single operating position along the longitudinal axis of the host boat, due primarily to inflexible or permanent mounting. When a boat is unloaded or loaded from one end, the center of mass moves along its length. While supporting the boat on its wheels, the operator must bear a portion of the weight of the boat and contents, which is proportional to the distance between the boat's center of mass and the axle position of the wheel assemblies.